While the prime minister continues to enjoy a Brown bounce with voters and the media, David Cameron has been warned he is facing a "summer of discontent".

The Brown bounce has worried some Tories

The warning, or threat, came from top Tory donor Lord Kalms who later turned up the pressure by clarifying his message to the party leader as "look chum, you need to do some re-thinking".

The pre-emptive strike, as Lord Kalms called it (and it is not his first), came as Mr Cameron was forced to defend his visit to Rwanda while his Oxfordshire constituency continued to suffer from the floods.

There have been suggestions he should have called off the visit to concentrate on the problems in his own back yard.

Mr Cameron insisted he was right to go ahead with the trip, saying issues like flooding, climate change and poverty could not be dealt with, without engaging with Africa.

But these were only the latest in what for him has been a run of bad headlines for Mr Cameron which followed the internal Tory row over the future of grammar schools.

Third place

That was seen as a presentational disaster and, it is claimed, led to the reshuffling of former education spokesman David Willetts, who started it all with a controversial speech claiming selection by ability did not work.

A breakthrough result in recent by-elections, particularly in Ealing Southall, might have given him the upper hand and ended the Brown bounce.

Mr Cameron's candidate proved controversial

In fact, despite small increases in the share of the vote, the Tories did worse than they hoped in both by-elections, with the candidate in Ealing Southall, Tony Lit - standing as David Cameron's Conservative - failing to pull off the predicted advance and ending in third place.

In the immediate aftermath of the polls, it was reported that two, and possibly up to six backbenchers had called for a vote of no-confidence in his leadership.

Mr Cameron dismissed that and said he was not taking such mutterings seriously: "I read the story and I just concluded that there was very little in it."

And it is absolutely the case that at any time it would be possible to find a handful of Tory backbenchers - or Labour or Lib Dem ones for that matter - ready to demand the removal of their leader.

Potential winner

In this case they were dismissed, probably accurately, by the Tory high command as "the usual suspects". And it is fair to say no sleep was lost over their anonymous threats.

So does any of this amount to a serious threat to Mr Cameron's leadership?

For a number of reasons, no.

Firstly, the rumblings against him are indeed mostly confined to that small group of "traditionalists" who have never supported him and who Mr Cameron is happy to take on as a symbol of his determination to move his party back onto the centre ground.

Mr Hague is reassuring right-wing on Europe

Secondly, most in the Tory ranks in Westminster appear to have had enough of routinely dumping their leaders, with all the divisions and distractions that inevitably encourages.

There remains a desire, just as there was with Labour and Tony Blair in the mid-1990s, to unite behind a man they see as a potential winner, despite some misgivings about his direction of travel.

And, while Mr Brown's early success has seemed to force the Tories onto the back foot, party bosses are reminding any jittery MPs that it was only to be expected and will probably not last. They should hold their nerve.

Secure future

Then there is the question of "if not Cameron, then who"?

Frontbenchers including Liam Fox and William Hague are currently out and about making speeches on issues like Europe and an opportunity society which may well be designed to reassure those on the right of the party.

But no one believes any of the right-wing candidates would currently stand a chance of replacing Mr Cameron, or are even planning to do so.

For the foreseeable future then - and that future lasts until the next general election - David Cameron seems secure.

However, and it is a significant however, he will want to have brought the Brown bounce back to earth well before then to avoid any fringe rumblings growing in intensity.